This invention relates to a floating-caliper disc brake, in particular for automotive vehicles, having a brake caliper straddling the edge of a brake disc, which is axially and slidably guided on arms of a brake carrier by means of spaced guide pins arranged parallel to the rotational axis of the brake disc and which is adapted to be supported on confronting supporting surfaces of the arms in the direction of rotation of the brake disc, and with brake shoes arranged on both sides of the brake disc and supported on the brake caliper in the direction of rotation of the brake disc, the brake shoes being actuated by a brake-actuating device arranged on one side of the brake disc.
In a known floating-caliper disc brake of the type referred to above as disclosed in U.S. Pat. No. 3,789,961, the brake caliper bears solely upon the supporting surfaces of the arms of the brake carrier in the direction of brake-disc rotation. The disadvantage of this arrangement is that on brake actuation the whole circumferential force transferred from both brake shoes to the brake caliper is transmitted to the rear arm of the brake carrier when viewed in the direction of brake-disc rotation, while the other arm of the brake carrier receives practically no load at all. Therefore both brake-carrier arms must be so dimensioned that they provide sufficient strength to receive the whole amount of circumferential force. Since in this known arrangement of the brakes, the brake caliper adjusts its position to the position of the supporting surface against which it abuts, the elastic deformation of the brake-carrier arm under the impact of the circumferential force causes misalignment of the brake caliper in relation to the brake disc and consequently wedge-shaped tangential wear on the brake shoe friction material. This effect is undesirable because it does not allow full use of the thickness of the friction material.
From British Pat. No. 1,194,567 a floating-caliper disc brake is known in which spaced guide pins are secured in the brake caliper when viewed in the direction of rotation of the brake disc, with sleeves being fitted onto the pins for axial sliding movement thereon and engaging into cups of a plate-shaped brake carrier aligned parallel to the brake disc, the cups being turned away from each other and outwardly open. The brake carrier includes a centric opening in which a brake shoe is guided and supported. A second brake shoe disposed on the opposite side of the brake disc is secured to the brake caliper. In this floating-caliper disc brake, the torque of the two brake shoes is transmitted to separate members of the brake carrier. The brake shoe which directly bears upon the brake carrier transmits its circumferential force to the rear area of the brake carrier when viewed in the direction of brake-disc rotation. The circumferential force of the brake shoe secured to the brake caliper, however, is transmitted to the brake carrier via the brake caliper and the front guide pin when viewed in the direction of brake-disc rotation. This arrangement results in an improved distribution of the load to the brake carrier. A disadvantage of this known floating-caliper disc brake is, however, the low alignment effect of the guiding of the brake caliper which may be the cause of substantial wedge-shaped wear of the brake shoe friction material. Further, the unilateral introduction of a circumferential force into the brake caliper by the brake shoe secured to the brake caliper makes it necessary to counteract the tendency of the caliper to turn about a radial axis by providing an offset of the two brake shoes in the peripheral direction. The counterforce produced by such an offset arrangement of the brake shoes must, however, be taken up by the brake disc, thereby causing an additional bearing pressure to be exerted on the brake disc.